Control device for a gearbox, in particular for a motor-vehicle gearbox, with a system for identifying the engaged gear

ABSTRACT

A control device includes an elongated mechanical transmission member ( 10; 110 ) interposed between the gearbox and a control member ( 100 ) for transmitting to the gearbox the commands imparted through the control member, in such a manner that the gear engaged by means of the gearbox is linked to the linear position of the transmission member ( 10; 110 ). The device is provided with a position sensor ( 26; 126 ) including a movable reference element ( 28; 128 ), the movement of which is univocally determined by the movement of a rigid end portion ( 14; 114 ) of the transmission member ( 10; 110 ), and a stationary detection element ( 30 ) for detecting the position of the reference element ( 28; 128 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a Divisional Application of U.S. application Ser. No. 12/811,194filed Jun. 29, 2010, which is a National Stage of InternationalApplication No. PCT/IB2009/050123 filed Jan. 13, 2009, which claimspriority from European Patent Application No. 08425017.4, filed Jan. 14,2008. The entire disclosures of the prior applications are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

The present invention refers in general to a control device for agearbox, in particular for a motor-vehicle gearbox, comprising a controllever operable by the driver and at least one elongated mechanicaltransmission member interposed between the gearbox and the control leverto transmit the engagement commands imparted by the driver through thecontrol lever to at least one engagement member within the gearbox, andmore particularly to a system for identifying the engaged gear to beinstalled in a gearbox control device to provide a signal indicative ofthe gear currently engaged.

The term “elongated mechanical transmission member” used above is to beintended as referred, in the following description and claims, to anymechanical member able to transmit a command by means of a translationalmovement. Such a mechanical member may be either a rigid member,typically a rod, or a flexible member, typically a Bowden cable.

U.S. Pat. No. 6,569,45 discloses a control device for a bicycle gearboxincluding a flexible control cable for transmitting the commandsimparted by the rider through a shift lever mounted on the handlebar toa (front or rear) derailleur of the gearbox, as well as a system foridentifying the engaged gear, which system comprises a movable memberdirectly secured to the control cable and provided with a movablecontact, a tubular housing mounted between two sheath sections withinwhich the control cable is slidable and conductive tracks provided onthe surface of a cavity of the housing along which tracks the movablecontact is slidable, in such a manner that the linear position of thecontrol cable, and hence the engaged gear, can be assessed by measuringa change in the electrical resistance resulting from the displacement ofthe movable contact along the tracks. However, such a system foridentifying the engaged gear has the drawback that it requires to mountthe movable member directly on the control cable and can therefore beused only in a gearbox control device provided with a flexible,push-pull cable, i.e. a flexible cable which is guided both in thepulling direction and in the pushing direction. Therefore, it cannot beinstalled at the ends (either on the side of the control lever or on theside of the gearbox) of the control cables of the usual control devicesfor motor-vehicle gearboxes, as these ends are formed by rigid rod-likeportions which have to be suitably guided and supported and thus cannothave movable members directly mounted thereon.

EP-A-0 820 926 discloses a control device for a bicycle gearboxincluding a control cable arranged to transmit to a rear derailleur ofthe gearbox the commands imparted by the rider through a shift knobmounted on the handlebar and a system for identifying the engaged gear,which system comprises a movable member provided with a magnet directlymounted on the control cable and a contactless magnetic position sensor(including for example a plurality of Hall sensors) arranged to detectthe position of the movable member. In addition to the drawback that itcannot be installed on the rigid end portion of a control cable of agear shift control device of a motor vehicle due to the same reasons asthose explained above, the system for identifying the engaged gear whichis known from the above-mentioned European Patent application has thedrawback that the mounting of a magnetic movable element on a steelcontrol cable involves the magnetization of the cable and hence a lossin the sensitivity of the sensor.

EP-A1 154 174 discloses a control device for a motor-vehicle gearboxcomprising a control lever operable by the driver, a servomechanism forassisting the engagement commands imparted by the driver by means of thecontrol lever and a cable connecting the control lever with theservomechanism. The servomechanism comprises an actuating rod, a gearmotor for driving the translational movement of the actuating rod underthe control of an electronic control unit, a control rod mounted so asto be able to translate parallel to the actuating rod, a connectinglever which is articulated at an intermediate point thereof by means ofan articulation pin to the actuating rod, is connected at a first endthereof to the cable and is connected at the opposite end thereof bymeans of a universal joint to an end of the control rod, and adisplacement sensor associated to the end of the control rod opposite tothe end connected power rod. When the driver operates the control lever,the electronic control unit controls the motor to generate an assistingforce on the actuating rod on the base of the signal provided by thedisplacement sensor as a result of the displacement of the control rodwhich is connected to the cable through the connecting lever. Since theconnecting lever is not stationary, but moves itself as a result of themovement imparted to the actuating rod by the gear motor, thedisplacement of the control rod detected by the displacement sensor doesnot correspond, i.e. is not univocally linked, to the displacement ofthe cable. The control device therefore requires an additional sensorarranged to provide the electronic control unit with a signal indicativeof the engagement position of the gearbox.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a system foridentifying the engaged gear for a control device for a gearbox, inparticular for a motor-vehicle gearbox, which is simple, not expensiveand reliable, which can be installed on the motor vehicle at any timeafter the manufacturing without the need to replace existing parts ofthe control device and which can be used with any control device for agearbox having at least one elongated mechanical transmission memberinterposed between the gearbox and a control lever operable by thedriver to transmit the engagement commands imparted by the driverthrough the control lever.

This and other objects are fully achieved according to the invention byvirtue of a control device for a gearbox, in particular for amotor-vehicle gearbox, having the characteristics described and claimedherein.

Further advantageous characteristics of the invention are set forth inthe dependent claims.

In short, the invention is based on the idea of providing a positionsensor arranged to detect the position of an elongated mechanicaltransmission member, be it either rigid (such as for example a rod) orflexible (such as for example a Bowden cable), which is interposedbetween the gearbox and the control lever and the position of which isrepresentative of the engaged gear, wherein the position sensorcomprises a movable reference element, the movement of which isunivocally determined by the movement of the elongated mechanicaltransmission member, as well as a stationary detection element fordetecting the position of the reference element, and wherein thereference element is mechanically connected to a rigid end portion ofthe mechanical transmission member (either on the side of the controllever or on the side of the gearbox) and is spaced apart from thatportion.

According to a first embodiment of the invention, the position sensor isa linear position sensor (of either contact or contactless type) mountedin parallel to the rigid end portion of the mechanical transmissionmember. In this case, the movable reference element of the positionsensor includes a connection portion secured directly to the rigid endportion of the mechanical transmission member and a sliding portionslidably mounted within the stationary detection element along adirection parallel to the axis of the rigid end portion, but spacedapart therefrom. It is thus possible to use a reference element providedwith a sliding portion of ferromagnetic material, without the risk ofmagnetizing the rigid end portion of the mechanical transmission memberand hence of negatively affecting the sensitivity of the positionsensor. Moreover, thanks to the fact that the reference element is notdirectly mounted on the rigid end portion of the mechanical transmissionmember, this latter can be freely guided and supported in the specialguide end portion provided in all the common control devices having aflexible cable.

According to a second embodiment of the invention, the position sensoris an angular position sensor and the reference element is a rotatablemember connected to the mechanical transmission member via a motionconversion mechanism for converting the translational movement of themechanical transmission member into a rotational movement of therotatable member. The same advantages as those indicated above for thefirst embodiment also apply to the second one.

BRIEF DESCRIPTION OF THE DRAWINGS

Further characteristics and advantages of the invention will becomeapparent from the following detailed description, given purely by way ofnon-limiting example with reference to the appended drawings, in which:

FIGS. 1 and 2 are a perspective view and a plan view, respectively, of arigid end portion (on the side facing a control lever) of a flexiblecable for the transmission of the commands from the control lever to amotor-vehicle gearbox provided with a system for identifying the engagedgear according to a first embodiment of the invention;

FIG. 3 is a perspective view of a rigid end portion (on the side facingthe gearbox) of a flexible cable for the transmission of the commandsfrom the control lever to a motor-vehicle gearbox provided with a systemfor identifying the engaged gear according to a first embodiment of theinvention; and

FIGS. 4, 5 and 6 are a perspective view, a plan view and a sideelevation view, respectively, of a rigid end portion (on the side facingthe control lever) of an elongated mechanical transmission member forthe transmission of the commands from the control lever to amotor-vehicle gearbox provided with a system for identifying the engagedgear according to a second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

With reference first to FIGS. 1 and 2, a control device for amotor-vehicle gearbox includes a flexible elongated mechanicaltransmission member which is generally indicated 10 and is arranged totransmit the engagement commands imparted by the driver, through acontrol lever (per-se-known and not shown) manually operable by thedriver, to an actuating member inside the gearbox (also per-se-known andnot shown). In the illustrated example, the flexible elongatedmechanical transmission member 10 is a Bowden cable including a sheath12 and a flexible tension wire (not shown) slidably received within thesheath 12. At the control lever-side end of the tension wire there isattached a rigid rod-like element 14, part of which is slidably receivedin a guide sleeve 16 carried by an end connection member 18 mounted in awall 20 of a support structure 22 for supporting the control lever. Atits free end projecting from the guide sleeve 16, the rod-like element14 is connected to the control lever through a ball joint 24 in such amanner that the forward and backward tilting movements of the controllever in the engagement direction (corresponding to the longitudinaldirection of the vehicle in a traditional H-type gearbox) are convertedinto forward and backward sliding movements of the rod-like element 14,and hence of the tension wire. In each of the selection planes, thecontrol lever can assume first and second engagement positions, that is,a forward position and a backward position, respectively, in either ofwhich one respective gear is engaged, as well as a neutral intermediateposition in which no gear is engaged. Each of the above-mentionedpositions of the control lever in the engagement direction univocallycorresponds to a respective linear position of the rod-like element 14.

In particular, when so-called start-and-stop engine management systemsare used, which cause the engine to stop when the vehicle is in neutralin order to obtain a reduction in the fuel consumption of the vehicle,it is fundamental to precisely identify the neutral condition of thevehicle. To this end, the control device according to the invention isprovided with a system for identifying the engaged gear which basicallycomprises a linear position sensor 26 mounted in parallel to therod-like element 14 to detect the linear position of that element, andhence of the tension wire attached thereto, and thus to provide anelectronic control unit (not shown) with a signal indicative of theengaged gear.

In the example illustrated in FIGS. 1 and 2, the linear position sensor26 is of the contact type, but might of course be of the contactlesstype as well. The sensor 26 includes a movable reference element 28drivingly connected for translation with the rod-like element 14 and astationary detection element 30 provided with electrically conductivetracks (not shown) in order to detect the position of the movablereference element 28, and hence of the rod-like element 14. According tothe illustrated embodiment, the movable reference element 28 has anL-shaped configuration and includes a sliding portion 32 which isslidably arranged within the stationary detection element 30 and isprovided with a movable contact (not shown) sliding on the electricallyconductive tracks of the stationary detection element 30, and aconnection portion 34 secured directly to the rod-like element 14.Accordingly, the movement of the movable reference element 28 isunivocally determined by the movement of the rod-like element 14.Further constructional and functional details of the linear positionsensor 26 are not described herein, as they are widely known to theskilled person.

By virtue of the movable reference element 28 of the linear positionsensor 26 being drivingly connected for translation with the rod-likeelement 14, and hence with the tension wire of the Bowden cable, thesensor 26 detects the current position of the tension wire and providesthe electronic control unit with a corresponding signal on the base ofwhich the unit is able to ascertain the engaged gear. Moreover, sincethe rod-like element 14 of the Bowden cable does not slide directlywithin the stationary detection element 30, but the stationary detectionelement 30 detects the position of a movable reference element 28mounted in parallel to the rod-like element 14, the rod-like element 14can be freely guided and supported in the guide sleeve 16.

As mentioned above, the contact linear position sensor might of coursebe replaced with a contactless linear position sensor, which will alsohave a movable reference element drivingly connected for translationwith the rod-like element 14 of the Bowden cable, as well as astationary detection element mounted on the guide sleeve 16 or onanother stationary component of the control device. It is possible forexample to use a magnetic system, in which the movable reference elementis provided with a magnet and the stationary detection element isprovided with Hall sensors. In this case, since a sliding portion of themovable reference element is not directly mounted on the rod-likeelement, it is possible to avoid problems of loss in the sensitivity ofthe linear position sensor due to the magnetization of the rod-likeelement.

It is however possible to use any other type of contactless sensor, forexample an analogical or digital radiofrequency sensor. In this case,the movable reference element will be provided with a reflecting antennaand the stationary detection element will be provided with a modulator,a de-modulator and a radiofrequency signal transmitter.

A system for identifying the engaged gear having a linear positionsensor such as the one described above might also be applied to acontrol device for a motor-vehicle gearbox having a rigid elongatedmechanical transmission member, such as a rod, as in this case it wouldbe sufficient to drivingly connect the movable detection element of thesensor for translation with the rod and to mount the stationaryreference element of the sensor on a stationary component either of thecontrol device or of the gearbox.

An example of mounting of the linear position sensor 26 at thegearbox-side end of an elongated mechanical transmission member of acontrol device for a motor-vehicle gearbox is illustrated in FIG. 3,where parts and elements identical or corresponding to those of FIGS. 1and 2 have been given the same reference numerals.

Also in this case the transmission member 10 is a Bowden cable includinga sheath 12 and a flexible tension wire (not shown) slidable receivedwithin the sheath 12. Part of a rigid rod-like element 14 secured to anend of the tension wire is slidably received in a guide sleeve 16carried by an end connection member 18 mounted in a support structure 22fixed to the gearbox. At its free end projecting from the guide sleeve16, the rod-like element 14 is connected through a ball joint 24 to anactuating member (not shown) inside the gearbox in such a manner thatthe sliding movements of the tension wire, and hence of the rod-likeelement 14, in either directions are converted into translational ortilting movements of the actuating member in either directions. Thelinear position sensor 26 includes a movable reference element 28drivingly connected for translation to the rod-like element 14 and astationary detection element 30 secured to the guide sleeve 16 andarranged to detect the position of the movable reference element 28, andhence of the rod-like element 14. According to the illustratedembodiment, the movable reference element 28 has an L-shapedconfiguration and includes a sliding portion 32 slidably arranged withinthe stationary detection element 30 and a connection portion 34 secureddirectly to the rod-like element 14, in such a manner that the movementof the movable reference element 28 is univocally determined by themovement of the rod-like element 14, i.e. of the control lever.

A second embodiment of a system for identifying the engaged gear for acontrol device for a motor-vehicle gearbox according to the invention,which includes a control lever 100 (of which only a lower end portion isshown) manually operable by the driver and an elongated mechanicaltransmission member 110 arranged to transmit the engagement commandsimparted by the driver through the control lever 100 to an actuatingmember inside the gearbox, will be described now with reference to theexample illustrated in FIGS. 4 to 6. According to this example, thetransmission member 110 is a Bowden cable including a sheath 112 and aflexible tension wire (which cannot be seen in the figures) slidablyreceived within the sheath 112. At the control lever-side end of thetension wire there is attached a rigid rod-like element 114, which isconnected at its free end to the control lever 100 through a ball joint124, in such a manner that the forward and backward tilting movements ofthe control lever 100 in the engagement direction (corresponding to thelongitudinal direction of the vehicle in a traditional H-type gearbox)are converted into forward and backward sliding movements of therod-like element 114, and hence of the tension wire.

In the system for identifying the engaged gear according to FIGS. 4 to6, an angular position sensor 126 is used which detects the angularposition of a rotatable reference element 128 connected to the rod-likeelement 114 via a motion conversion mechanism for converting thetranslational movement of the rod-like element 114 into a rotationalmovement of the reference element 128. More specifically, the motionconversion mechanism includes a shaft 140 connected at an end thereof bymeans of a ball joint 142 to a sleeve 144 secured to the rod-likeelement 114 and at the opposite end thereof by means of a gimbal joint146 to the rotatable member 128. The connection by gimbal joint 146between the shaft 140 and the reference element 128 allows displacementsof the rod-like element 114 in a direction perpendicular to the slidingdirection as a result of displacements of the control lever 100 in thetransverse direction among the various (usually three) selection planes.By virtue of the connection through the motion conversion mechanism, the(rotational) movement of the reference element 128 is univocallydetermined by the (translational) movement and the rod-like element 114,i.e. of the control lever of the gearbox. The angular position sensor126 detects directly the angular position of the reference element 128and hence indirectly the linear position of the rod-like element 114.The electronic control unit is therefore able to ascertain the engagedgear on the base of the position signal provided by the angular positionsensor 126. Also in this case, the constructional and functional detailsof the sensor 126 are omitted, as they are well known to the skilledperson.

The arrangement with an angular position sensor can be equally wellapplied to a control device for a motor-vehicle gearbox having a rigidelongated transmission member, even though the arrangement with a linearposition sensor described above with reference to FIGS. 1 to 3 ispreferable for reasons of size, simplicity of construction and cost.

Naturally, the principle of the invention remaining unchanged, theembodiments and constructional details may vary widely with respect tothose described and illustrated purely by way of non-limiting example.

For example, instead of being manual, the control device might also berobotized, in which case the elongated mechanical transmission memberwould be interposed between the gearbox and an actuator which iscontrolled by the electronic control unit governing the operation of thegearbox.

The invention claimed is:
 1. A control device for a gearbox, comprisingan elongated mechanical transmission member interposed between thegearbox and a control member for transmitting to the gearbox thecommands imparted through the control member, in such a manner that theengaged gear is linked to the linear position of the transmissionmember, wherein the transmission member includes a rigid end portion,wherein the device is provided with a linear position sensor comprisinga movable reference element and a stationary detection element arrangedto detect the linear position of the reference element, wherein themovable reference element is mechanically connected to the rigid endportion and spaced apart from it, so as to be connected for translationwith the transmission member, wherein the transmission member is aflexible transmission member including a sheath and a tension wireslidably received within the sheath, the rigid end portion having arod-like element attached to an end of the tension wire, and a guidesleeve for guiding said rod-like element, and wherein the stationarydetection element is mounted on the guide sleeve.
 2. The device of claim1, wherein the linear position sensor is a contact linear positionsensor, the stationary detection element being provided withelectrically conductive tracks and the movable reference element beingprovided with a movable contact sliding on the electrically conductivetracks of the stationary detection element.
 3. The device of claim 1,wherein the linear position sensor is a contactless magnetic sensor, themovable reference element being provided with a magnet and thestationary detection element being provided with Hall sensors.
 4. Thedevice of claim 1, wherein the linear position sensor is a contactlessanalogical or digital radiofrequency sensor, the movable referenceelement being provided with a reflecting antenna and the stationarydetection element being provided with a modulator, a de-modulator and aradiofrequency signal transmitter.
 5. The device of claim 1, wherein themovable reference element has an L-shaped configuration and includes asliding portion which is slidably arranged within the stationarydetection element and a connection portion rigidly connected to therigid end portion.